The present invention relates generally to the field of semiconductors and more particularly to an alignment wafer for a semiconductor processing tool.
Integrated circuits are formed on semiconductor wafers. These wafers are processed by a number of different stations. For instance, one station may be a photographic station where the photoresist is exposed. A second station may be developer station that washes away the photoresist that is unexposed (exposed in another variation). When a semiconductor wafer is not correctly aligned on a chuck (commonly vacuum) of one of the processing stations, the pattern may be incorrect and the underlying circuit will not work. This results is substantially economic loss to the manufacturer. One solution has been to create alignment wafers made of aluminum. This allows the operator to check that the wafer is correctly aligned. Unfortunately aluminum alignment wafers bend easily and then they do not sit in the processing station correctly. Another solution has been to use glass alignment wafers. Glass wafers have a tendency to break and are heavier than semiconductor wafers. Because they are heavier they cannot be held in place by the vacuum chucks as well. One other solution has been to use carbon fiber wafers. These are not transparent and as a result are difficult to align to the chucks.
Thus there exists a need for alignment wafer that can overcome these problems.